1. Field of the Invention
The present invention is directed to an aspirator having a muffler, and, more specifically, toward an aspirator having an aspirator chamber and a muffler chamber connected by a duct with at least a portion of the aspirator chamber and a portion of the muffler chamber being formed from a unitary body of material.
2. Description of Background Art
Modern automobiles often include climate control systems that automatically adjust a vehicle cabin temperature in order to establish and subsequently maintain the temperature at a level set by a user. Such systems include temperature sensors that provide information on current cabin temperature to a system controller, and the controller controls the vehicle heater and/or air conditioner in a well-known manner based on the sensed temperature.
Temperature sensors are often recessed in an instrument panel or otherwise disposed in an out-of-the way location that may not be exposed to air representative of cabin-temperature air. For example, a sensor mounted beneath a dashboard that has been exposed to the sun while the vehicle windows are open may detect a temperature hotter than the actual temperature of the cabin. Likewise, a sensor may be shaded and remain cool for a period of time after the interior of the vehicle has risen to an uncomfortably warm temperature. It is therefore known to provide a mechanism to draw air from the cabin past the temperature sensor in order to expose the temperature sensor to air representative of an actual cabin temperature.
One type of device for drawing air past a temperature sensor is an aspirator, and a conventional aspirator is illustrated in FIG. 11. The aspirator includes a generally T shaped housing 300 having an outlet 302 at the end of one arm of the T-shaped housing 300, an aspirator inlet 304 at the end of the other arm of the T-shaped housing and in inlet tube 306 forming the base of the T-shaped housing. The housing narrows between the inlet tube 306 and the outlet 302 to form a venturi section 308. Air flowing from the inlet tube 306 toward outlet 302 speeds up as it passes through the narrow venturi section 308, and this more-quickly moving air has a lower pressure than the slower moving air in the other parts of the housing 300. The low pressure draws or aspirates air into the T-shaped housing 300 via aspirator inlet 304. Suitable tubing 310 is connected to aspirator inlet 304 and runs to a location behind a vehicle instrument panel (not illustrated) where a temperature sensor 312 is mounted. Thus, when air from the vehicles HVAC system is blown into the vehicle cabin through inlet tube 306 and outlet 302, this moving air also draws ambient cabin air into the tubing 310 and past the temperature sensor 312.
Noise is generated as air passes through venturi section 308, and this noise and further sounds from the HVAC system, may be transmitted along tubing 310 into the vehicle cabin. To reduce such sounds, which may be objectionable to passengers, a muffler 314 may be mounted between the aspirator housing 300 and the temperature sensor 312. This muffler may include foam on its inside to further reduce noise levels. Furthermore, it is sometimes necessary to wrap the muffler 314 with foam to reduce noise produced by movements of the muffler. Present designs thus require at least three elements to draw air over a temperature sensor: an aspirator, a muffler, and tubing to connect the aspirator and the muffler. It would be desirable to provide an improved system for drawing air over a temperature sensor that is effective and easier to manufacture than conventional multi-element systems while at the same time providing equivalent or improved airflow and noise reduction.